The atomic resolution structures of viruses provide a new framework for studying the interaction of viruses with their cellular receptors, designing anti-viral therapeutics, and understanding the bonding interactions in complex macromolecular assemblies. Although these structures represent well-resolved end-products, the process of virus assembly remains ill-defined with regard to its regulation within virus-infected cells and the properties of the viral structural proteins which determine the pathways of assembly. The study of virus assembly has direct implications for designing anti-viral therapies, but also has relevance to the general biologic problems of protein folding, protein trafficking within cells, and the interaction of eukaryotic chromosomes with structural proteins. The aims of this proposal are directed at understanding the structure and assembly of polyoma and papillomaviruses at the atomic, biochemical, and cell biological levels. Atomic resolution structures of human papillomavirus (HPV) subtypes-11 and 5 L1 capsid proteins, HPV L1+L2 capsid protein complexes, and bovine papillomavirus virions will be determined. The role of the polyoma and papillomavirus minor capsid proteins, VP2/3 and L2, in capsid assembly and stability will be assessed using an in vitro assembly system. The cell chaperone proteins hsc70/DnaK and karyopherin proteins involved in nuclear transport will be analyzed for their ability to regulate in vitro capsid assembly. The ability of SV40 large T-antigen to function as an hsp40 analog will be characterized in chaperone-mediated capsid assembly in vitro and in vivo. Finally, using SV40 VP1+VP3 proteins complexed with hsc70, capsid assembly will be coupled with in vitro replicating SV40 viral minichromosomes to recapitulate complete virion assembly in a reconstituted system. The goal is a comparison of polyoma and papilloma assembly strategies and virion structures to identify general principles in virus construction and targets for therapeutic intervention.